1. Field of the Invention
The present invention relates to metal wall framing systems, and, more particularly, to a drainage valve system for mullions of a wall framing network.
2. History of the Prior Art
Metal wall framing systems are conventional for fabrication of high-rise commercial structures and the like. In such systems, elongated metal elements--mullions, sills, jams etc.--grip the edges of opaque or transparent panels of various thicknesses to form a coherent wall, either of the store front type or of the curtain wall variety. Typically each mullion comprises an aluminum extrusion providing a variety of cross-sectional configurations, many specially adapted for the particular building fenestration application in water intrusion conditions. Double panel, extruded metal frames, for example, generally incorporate multiple interior chambers and exterior side flange portions. The frame is usually formed of extruded aluminum with a plurality of wind and water seals which afford many advantages over conventional window and door frame constructions These advantages include cost, strength and reduced maintenance. Among the disadvantages of metal, however, is the effectiveness of water intrusion sealing and the provision for elimination of intruded water contained within the hollow mullions.
There are many sources of intruded water in the horizontal and vertical mullions of a curtain wall network. For example, one source is rain water and window washing water which leaks past panel gripping gaskets. Another source of intruded fluid is condensation from moist air within the hollow channel regions of the mullions. Larger quantities of intruded water which is in the portions of the mullions that are exterior of the panels can be disposed of fairly readily by means of open weep holes and the like. However, such weep holes also provide means for moisture infusion back into the mullion. Moreover, water infiltration under high force winds can cause high pressure turbulence within the glazing cavity of the mullion. If sufficient water is permitted to ingress into the hollow mullion regions, along with such turbulence, it will ultimately leak into the interior of the building panels. The water will then be discharged into the interior of the building which is always objectionable and very often causes damage. It is therefore an advantage to effectively discharge all water contained within the mullions prior to any substantial accumulation and to prevent high pressure turbulence therein.
The prior art is replete with various methods and apparatus for the self draining of hollow mullion regions and the like and many of these configurations incorporate the use of flap-valve members. For example U.S. Pat. No. 3,503,169 issued to Johnson et al. on Mar. 31, 1970 describes a self-draining window sill incorporating a valve closure member. The flap-valve element is a substantially flat, rigid member having an upper hinged portion adapted for swinging into a type of abutting contact with an adjacent weep hole or slot formed within the horizontal mullion.
The flap valve approach of the prior art is particularly advantageous because wind pressure against an exposed weep hole can drive water inwardly through the hole and upwardly between the various assembled members of the building fenestration causing both water infiltration and turbulence. The force of the wind against the curtain wall having flap valves will force closure of the valve member to substantially prevent infusion of water. Such valve members are taught in early prior art window sill constructions as set forth in U.S. Pat. No. 2,827,674 issued to Hauck on Mar. 25, 1958 for "Scuppers". This patent illustrates a hinged cover plate adapted for engaging a conventional weep hole to prevent water from being driven therein by wind, rain and the like. Again, a substantially rigid flat plate is incorporated with a hinge mechanism for forming the ventilation aperture. U.S. Pat. No. 3,199,156 issued to Riegelman on Aug. 10, 1965 likewise shows the weep hole construction for windows and the like utilizing a flat member formed of rubber which permits the egress of water through a lower channel region. The cover flap is flexible and pivots along one edge throughout the length of the upstanding flange such that the flap extends generally downward to cover most of the weep hole. Once sufficient fluid accumulates, the pressure will cause the flap to move outwardly about the pivot axis and the groove as shown in that patent reference to allow the fluid to drain.
While the aforesaid prior art embodiments are effective in a myriad of applications, numerous problems still remain relative to high performance demands of water infiltration and drainage with advanced construction designs. Typical structural systems providing a framework adequate to meet the wind loads of conventional curtain walls with silicate seals around the perimeter of each panel are strict and uncompromising. Human error is a constant factor in long term reliability in such constructions. If a seal fails integrity of the wall is compromised and damage to interior trim and furnishings is inevitable. Though the hinged flap approach has been effectively utilized in many instances there is generally no provision made for inducing water collected within a hollow mullion to drain through the weep hole. Moreover, the surface tension of the water often creates a meniscus within the weep hole effectively damming fluid inside the mullion and preventing its escape. Wind and other moisture bearing against the weep hole and panel seals and then infiltrating therethrough can aggravate the already deleterious situation. Such situations can cause existing water accumulations to increase. Even when the water accumulation does not infiltrate the building interior, its very presence within a hollow mullion creates a serious problem. The moisture of the collected water has a tendency to attack the cement used to seal conventional insulated glass in such curtain wall structures. The glass manufacturers are extremely sensitive to designs which permit moisture to lie in the vicinity of a glazing cavity even when said moisture is not in direct contact with the seal of the window. In certain instances, the water vapor and/or condensation can ultimately cause deterioration in the cement and in some situations the glass manufacturer's warranties may even be voided. It is, therefore, of tantamount import that the hollow mullions be constructed in a design not only facilitating egress of water accumulations but effectively urging water deposits to be eliminated.
Pressure differentials between the interior of the building and the outside of the building provide some inducement for fluid flow within the hollow mullions of prior art systems. However, few conventional systems provide the combination of effective sealing mechanisms and means for a pressure differential flow response. This is a distinct need. Without means for inducing water contained within the mullions to flow out, prior art structures are functionally deficient in high moisture, high wind areas such as monsoon regions of the world. Curtain wall constructions are, however, generally accepted construction techniques around the earth. It would be an advantage, therefore, to provide an improved curtain wall sealing and drainage system for conventional, hollow mullion curtain wall constructions.
The method and apparatus of the present invention provides such an improved drainage system for curtain wall structures wherein a weep hole for a hollow mullion is covered by a resilient flap secured thereabove for imparting a substantially flush engagement of the flap against the surface area around and beneath the weep hole. In this manner fluid contained in the mullion and disposed beneath the flap is induced to migrate downwardly through "the capillary force" of the water sealed beneath the resilient flap and against the weep hole and through a "syphoning" action then created. In this manner water contained within the mullion is induced to flow outwardly therefrom for discharging the undesirable fluid content. Unlike prior art configurations, the resilient flap is sealed in a flush conforming configuration against the weep hole and the area therearound in a manner adapted to form a capillary stream in sealed communication with the interior of the mullion. This method of inducing fluid flow is likewise efficient in preventing the infiltration of water and air turbulence from wind bearing thereagainst, yet is responsive to pressure differentials for permitting the discharge of fluids within the mullion due to a lower atmospheric pressure outside the building.